The subject invention concerns a device for indication of a predetermined tension of elongate flexible elements, primarily of belts incorporated in belt transmissions, e.g. driving belts used in combustions engines and running around belt pulleys to drive the generator, the radiator fan, the servo pump, air conditioning unit, etcetera.
During the assembly of new as well as reconditioned combustion engines, it is customary to simultaneously install the driving belt or belts driving the equipment items mentioned above. In a manner similar to that used when worn-out belts are replaced by new ones, these belts are placed loosely around the various pulleys with the adjustment device of e.g. the generator in a non-tightened condition. The set screws of the adjustment device is then tightened by means of a suitable tool, such as a screwdriver, while at the same time the belt is tightened by means of another suitable tool, e.g. a lever acting on the generator so as to force the latter outwards. The magnitude of the belt tension is usually checked by the operator who, for instance with the aid of his thumb, depresses the belt at a point intermediate two adjacent pulleys, and the tightening force or belt tension is normally considered to be "correct" if the force exerted on the belt in this manner amounts to a depression corresponding approximately to 10 mm.
However, this method does not make it possible to ascertain with sufficient certainty the actual value of the belt tension, in addition to which the tension may vary within very wide limits from one engine to the next. Some belts therefore wear out prematurely as a result of slippage.
Since in modern engines, particularly motor vehicle engines, the driving belts are dimensioned for a comparatively long serviceable life, which is a feature requested by the consumer, it is necessary to make arrangements ensuring that a value of the tensional force may be achieved in a reproduceable manner and at a carefully predetermined level with only very minute tolerance deviations.